totally not true, there are point of no returns even for things that have once been avoidable but are not anymore after a certain momentum in relation to the inertia of a given system has been reached.

If you are referring to the Arctic, there is no point of no return. Even if we attain a BOE condition, the Arctic will re-freeze (and glaciers expand), if temperatures dictate such. This is simple physics.

i refer to what you referred and then a return path that would exceed the live span of several generation and/or take longer than mankind exists is NOT a turnaround that deserves that term.

matter of factly, yes, there can be a next ice-age, we cannot discard the possibility, but it's obvious that this is now what is meant with "point of no return" it means that if we reduce pollution to zero today, that we probably won't live to see that turn-around and if the planet shall recover once we're extinct that was not the point that is discussed in the context of reverting the process be free will and human action or literally lack of action

BTW i'm in the 2020-20125 ballpark while 2020-2030 would have been my favourite choice because it's almost impossible to make an educated guess that is more accurate than a decade.

totally not true, there are point of no returns even for things that have once been avoidable but are not anymore after a certain momentum in relation to the inertia of a given system has been reached.

If you are referring to the Arctic, there is no point of no return. Even if we attain a BOE condition, the Arctic will re-freeze (and glaciers expand), if temperatures dictate such. This is simple physics.

I think it"s pretty clear that this thread is about predicting the next BOE. No one is suggesting that the next BOE will be the last one the earth will ever experience.

totally not true, there are point of no returns even for things that have once been avoidable but are not anymore after a certain momentum in relation to the inertia of a given system has been reached.

I am one of the two that chose 2041-60.

If you are referring to the Arctic, there is no point of no return. Even if we attain a BOE condition, the Arctic will re-freeze (and glaciers expand), if temperatures dictate such. This is simple physics.

I think it"s pretty clear that this thread is about predicting the next BOE. No one is suggesting that the next BOE will be the last one the earth will ever experience.

This will be a disaster for polar bears. They will not be able to escape in Canada and Greenland, and all will drown near the North pole.

That's not going to happen. But there is no way that Arctic sea ice loss will be good for polar bears.

Why do you think this is unlikely? You wrote last year how the Northern shores of Greenland were cleared of ice at the end of August. It is obvious that there is a high probability that polar bears will fall into the ice trap in the Central Arctic and die.

google how far and how long polar bears can and do swim, even when they don't necessarily have to, you'll be surprised and know why this won't happen the way you describe.

neven's take on this is as spot on as it can get. bad for the bears but they won't drown in numbers.

Bears will be able to swim hundreds and thousands of kilometers, even in conditions of multimeter waves?

After all, most likely the complete melting of ice in the Arctic will happen after a powerful cyclone, like those that happened in August 2012 and 2016.

In such conditions, bears trapped will have very little chance of escape. It should be understood that only with warming in the Arctic increases the height of the waves, to which the bears will not have time to adapt.

since the ice he stands on won't disappear withing a few hours he shall choose the moment to begin his journey carefully.

i feel it, that you have a point and wand recognition and if i do others do as well and others don't but either way it can become annoying.

what's next, after the storm argument? the sun blinding him or anything of that kind.

fact is that all this sounded from the beginning like if we would gonna face a mass drowning which we most probably won't for the said reasons and everything is instisting blahhh... to be right.

there are many enough real catastrophies at hand, you can freely choose among them. exagerations have never been helpful to make a point LASTING.

short term effects can be achieved among the sheep but then once it doesn't happen the storm sawn is blowing back into the seeder's faces. backfiring for the cose so to say.

yes, the p'bears are at risk and they are losing out on space to feed and to procreate but they won't drown in masses for the reasons you stated because the reason won't happen that way any time soon and the effect won't be as you suggest.

Tealight prompted me to do some extra work on the High Arctic (the 7 central seas), as that is where ice-free will happen last. (It was his stupendous work on Alebo Warming Potential that was the trigger).

So I updated my open-water graphs to add a "high arctic" trend graph.. I attach 2 graphs, on for the high arctic and one for the total Arctic.

The High Arctic graph shows that even at the peak of the melting season, open water only reached 50% by the year 2000, and also that these seas are still an icy desert in Winter, barely touched by global heating.

It is graphs like these that reinforce my conviction that:-- decline in Arctic Sea Ice is remorseless and inevitable,- the BOE is still a few years away,- when a BOE arrives may be a function more of volume loss.

So I still plump for a BOE before 2030, but perhaps at the end of the 2020s.

I would not be surprised if we have a year soon (any year including this year) where the numbers still say 2-3 million sq km at the end of the melt season, but the condition of the ice - fragmented, slushy, dispersed and mobile - is qualitatively unlike anything in the satellite record.

Nice graphs. However, I question your trend lines. Both the max and min were decreasing fairly constantly for the first decade. However, both max and min have been flat over the past decade.

Max certainly hasn't been flat over the last decade, seems to be following the trendline pretty faithfully. And besides, trendlines are what trendlines do - and I doubt very much whether the difference between the last decade and the previous two is in any way statistically significant.

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because a thing is eloquently expressed it should not be taken to be as necessarily trueSt. Augustine, Confessions V, 6

Nice graphs. However, I question your trend lines. Both the max and min were decreasing fairly constantly for the first decade. However, both max and min have been flat over the past decade.

This is consistent with the observation made by Crandles that there was a state change in 2010 when the Arctic lost a ton of volume (the thickest ice) which was not fully reflected in the extent numbers. Since 2010 we have been in a relatively static condition where FYI is created each freeze season and melts out each melt season.

This is very likely the same cherry as "No warming since 1998!" or the hiatus, but because the next state change hasn't happened I will do it. All that needs to happen for this line to come true is that in a warming world Arctic ice doesn't melt faster. It could happen, but I wouldn't bet the fate of our civilization on it.

The state change can be appreciated on attachment one. From 2000-2012 the Loss to Max ratio increased almost monotonically, then after 2012 the Loss to Max Ratio flattens. I drew a 6 year moving average that shows the behavior I'm attempting to show.

It seems that in the "High Arctic" the state change began in 2012. Thus I'm ignoring all previous years to 2012 and I'm drawing the line using only the years after 2012. I'll update after the next minimum is reached.

I think we all see the same thing here: The loss flatlines and even seems to drop. Which may very well be indicative of a real state change and not a statistical fluke. I think it may very well be the former, but the datapoints are too few to statistically validate any change in trends.

You mention the "hiatus" that some people see in the warming data, and yes it's there and easy to see - but as Tamino has pointed out, even with a dataset stretching over more than 100 years, a ten year "flatline" is not statistically significant.

Besides, the constant drop in the max line does not show any state change, simply business as usual, so the theoretical state change does not show up in the max numbers? And yes, I do think there may very well have been a state change, but the numbers are not conclusive.

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because a thing is eloquently expressed it should not be taken to be as necessarily trueSt. Augustine, Confessions V, 6

I think it is better to show data from beginning than selecting 2000 as starting point.

Note: I don't believe the completely flat trendline at the end, I think it will continue downwards but at a fairly slow rate.

Is it straight or curved? Perhaps not clear enough to be statistically significant, particularly with April.

While residuals are uncorrelated, I think there is still good reason to think shape of trendlines will be somewhat similar between April and Sept: Less volume means more area becomes thin ice and open water so albedo drops and more energy is absorbed ....

If curved then the way this shows seems to be the way it is going.

Also an understanding of the data and processes helps draw conclusions. When Piomas and other models were run with huge initial step change, half the ice thickness at beginning of melt season the models showed that some ice remained. So the models had very little ice loss in such a year. If this is where we are going then the curves I show (but still going a little down at the end) are more like what we should expect.

We are at the beginning of a massive conversion event. Why would the sea ice find a new equilibrium this early in the process? Doesn't sound logical to me.

horizontal extrapolation would indeed be magical, and I don't believe that as noted. This question was about shape of trendline not of the extrapolation. Which is better fit straight diagonal line though data or curve I have drawn? (obviously curve but that is of course capable of fitting data better with more parameters/degrees of freedom. Sorry if this wasn't clear.

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b_lumenkraft

This question was about shape of trendline not of the extrapolation. Which is better fit straight diagonal line though data or curve I have drawn? (obviously curve but that is of course capable of fitting data better with more parameters/degrees of freedom. Sorry if this wasn't clear.

I think it is better to show data from beginning than selecting 2000 as starting point.

PIOMAs regional starts on the year 2000, so I didn't select a starting point , I used all the data available to me.

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Note: I don't believe the completely flat trendline at the end, I think it will continue downwards but at a fairly slow rate.

Is it straight or curved? Perhaps not clear enough to be statistically significant, particularly with April.

I think annual volume losses will go up slowly, while the max keeps steadily and linearly marching down. Then one year, when the ice is thin enough and we get unlucky with the weather then the September minimum will go to 0. After that minimum will hit 0 every year.

2012 was a record loss year, so starting the graph for the changed state on 2012 has the effect of creating an artificially declining slope. Attached the graph with the new trend line starting in 2013.

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While residuals are uncorrelated, I think there is still good reason to think shape of trendlines will be somewhat similar between April and Sept: Less volume means more area becomes thin ice and open water so albedo drops and more energy is absorbed ....

They are mostly linear, the maximum showing very good linearity and the minimum staying within acceptable limits of linearity. This is so because the behavior of this system is due mostly to the Sun or lack thereof and Earth's orbit and tilt. For the purposes of Arctic freeze/melt cycles, that energy is mostly constant. The variation that we see year to year is mostly weather. The constant downtrend is due to GHG's

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If curved then the way this shows seems to be the way it is going.

I think this is the exact opposite of what the physics indicate. The world is warmer, the ice is thinner, the water saltier and the pack has loss significant mechanical strength. I see no reason why losses should slowdown for much longer.

Unless something changes drastically this melting season (very good chance for that), it seems your straight line case may get a mortal blow this year.

As the volume goes down losses must go down. There is simply less ice to melt, and certainly less easy peripheral ice to melt.With the disappearance of multi-year ice, volume loss must go down as well.But all this doesn't mean that volume is expected to reach equilibrium. The curve will surely go down, only question is how quickly or slowly.

As the volume goes down losses must go down. There is simply less ice to melt, and certainly less easy peripheral ice to melt.With the disappearance of multi-year ice, volume loss must go down as well.

Only if you hold temperature, salinity, export and thickness constant. If the effect on the ice of any/all of these variable is of larger magnitude than the lack of ice to melt it must go up.

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I am an energy reservoir seemingly intent on lowering entropy for self preservation.

Since such dates has gompertz or straight line been a better predictor?

.

As thickness at max reduces and approaches a meltable thickness, the loss goes up as albedo goes down. Once under the meltable thickness then the volume loss in that area goes down and temperature goes up. Over time more and more of the area gets under the meltable thickness so there is certainly the potential for the volume loss to go down. Temperature goes up but it is in wrong places to melt ice so it has to increasingly travel further. It isn't clear whether this temperature increase overcomes the reduction in available ice to lose effect. However the pattern seems to be that there was increase in volume loss but perhaps it is now going down.

I don't think this is conclusive either way, but if you think the loss will continually increase then the shape of the loss trends seems a bit odd (not definitely ruled out but a bit odd). If you think the loss will increase then decrease again there is nothing particularly odd in the shape of the volume loss data.

As the volume goes down losses must go down. There is simply less ice to melt, and certainly less easy peripheral ice to melt.With the disappearance of multi-year ice, volume loss must go down as well.But all this doesn't mean that volume is expected to reach equilibrium. The curve will surely go down, only question is how quickly or slowly.

Exactly! Piomas Sept. volume is one-third of what is was in 1980. The Arctic simply does not have as much ice to lose. Hence, volumetric losses will continue to decrease. Equilibrium will not occur, unless the climate holds steady for a prolonged period. The curve looks good, and likely to continue until a state change forces it to change.

Using the PIOMAS data that you posted previously, the trend line for the minimum volume since summer 2010 is +0.06 / yr and the maximum is -0.14 / yr, and neither is significantly different than zero. Considering that the linear trends for the previous decade were -0.73 and -0.46 for the min and max, I would say confidently that the recent trends are flat compared to the most recent declines. Using your data, I cannot substantiate it any more than that.

However the pattern seems to be that there was increase in volume loss but perhaps it is now going down.

Please, attempt to convince me it is currently going down. If we take 2013 as the starting point, a year firmly in the "new ice arctic" regime, it is going up. The melting season thread hints to going up even more.

In the mean time, I like to look at the following animation as a rough bounds for the possible futures.

The maximum is -0.14 / yr, and neither is significantly different than zero.

Your characterization of the maximum is plain wrong. The maximum has kept a steady decline , significantly higher than zero, even when there is much less thick and easy ice to melt.

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I would say confidently that the recent trends are flat compared to the most recent declines.

You can say it confidently with words, but not with numbers.

Max has been steadily going down even if we pick a very high starting point for the graph, like 2010. See attachment for lines, slopes and R2 of 2010 to present and 2001 to 2010. While it is true that if we pick 2010 the slope improved, it is marching steadily down, even in the absence of easy ice.

The maximum is -0.14 / yr, and neither is significantly different than zero.

Your characterization of the maximum is plain wrong. The maximum has kept a steady decline , significantly higher than zero, even when there is much less thick and easy ice to melt.

The maximum has kept a steady decline not because there is much less thick and easy ice to melt but that there is far more open stretches of water that has taken up additional heat from the sun to freeze.

The maximum is -0.14 / yr, and neither is significantly different than zero.

Your characterization of the maximum is plain wrong. The maximum has kept a steady decline , significantly higher than zero, even when there is much less thick and easy ice to melt.

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I would say confidently that the recent trends are flat compared to the most recent declines.

You can say it confidently with words, but not with numbers.

Max has been steadily going down even if we pick a very high starting point for the graph, like 2010. See attachment for lines, slopes and R2 of 2010 to present and 2001 to 2010. While it is true that if we pick 2010 the slope improved, it is marching steadily down, even in the absence of easy ice.

I am guessing that you are using daily ice volume, whereas I am using monthly. That is the only reason that I can see for the discrepancy.

Max has been steadily going down even if we pick a very high starting point for the graph, like 2010. See attachment for lines, slopes and R2 of 2010 to present and 2001 to 2010. While it is true that if we pick 2010 the slope improved, it is marching steadily down, even in the absence of easy ice.

Archimid,

You are exactly correct about the maximum values being on a steady decline. I would be careful though in arguing that the annual decline is now shrinking. There may be actual dynamics at work, such as the loss of thick ice to melt. It may equally be that you are only seeing an apparent trend where there isn't one, due to the statistics variations and randomness, or some longer period oscillation. The entire time series of annual loss from 1979 to the present is slowly increasing. The last few years decline does not appear to definitively be significant. A single year with larger loss (2019 may be that year), would dramatically change the chart and the conclusions.

It is time for the monthly update of my extrapolation when the extent [Extent], volume [Volumen] and thickness [Dicke] will reach zero. The extrapolation occured linearly and by a logarithmic function; the latter one almost constantly resulting in earlier times. May value now includes 2019. Extent value for May 2019 lies below, volume and thickness lie above the long-term linear trend lines. As these anomalies aren't too large, the "BOE numbers" haven't changed significantly compared to last year.

Please note that this is not a forecast but a trend!See attached table.

I think we all see the same thing here: The loss flatlines and even seems to drop. Which may very well be indicative of a real state change and not a statistical fluke. I think it may very well be the former, but the datapoints are too few to statistically validate any change in trends.

I think the loss flatlines (in the case of the Arctic) because total winter extent vs loss is reaching a hard limit - zero - as to how much ice is left over at the end of the melting season.

We have seen a decline in melt season total loss of extent and volume, but that remaining volume is (1) harder to reach and increasingly (2) isn't replaced during the refreeze.

The sun reaches the 80N at the same time, and has the same effect, but there is less ice at lower latitudes.

My instinct now is to watch the winter numbers more closely than summer's, as that's were I think the real harbingers to our first BoE will show up.

I think we all see the same thing here: The loss flatlines and even seems to drop. Which may very well be indicative of a real state change and not a statistical fluke. I think it may very well be the former, but the datapoints are too few to statistically validate any change in trends.

I think the loss flatlines (in the case of the Arctic) because total winter extent vs loss is reaching a hard limit - zero - as to how much ice is left over at the end of the melting season.

We have seen a decline in melt season total loss of extent and volume, but that remaining volume is (1) harder to reach and increasingly (2) isn't replaced during the refreeze.

The sun reaches the 80N at the same time, and has the same effect, but there is less ice at lower latitudes.

My instinct now is to watch the winter numbers more closely than summer's, as that's were I think the real harbingers to our first BoE will show up.

Its worth reminding ourselves that "from the comparison with in situ observations it appears that PIOMAS tends to overestimate thin ice and underestimates thick ice. As the ice thins such systematic errors can affect the overall trend."

magnamentis

Its worth reminding ourselves that "from the comparison with in situ observations it appears that PIOMAS tends to overestimate thin ice and underestimates thick ice. ...

the only thing that i know for sure is that PIOMAS overestimates any ice against no ice at all.

the current mid-month report shows ice north of point barrows that isn't there since 8th or 9th of June, depending on interpretation while currently there is a clear ice-free zone that is not showing at all in piomas maps.

this is not the only place, it's just a prominent, obvious and well know example since that spot has been subject to a poll an exiting race for the 7th that turned out to be the 8th IMO.

PIOMAS is calibrated to NSIDC sea ice concentration, which has coarse resolution (25x25km). Perhaps NSIDC shows this area with some ice?

That it uses NSIDC concentration is good information.I've been comparing the latest modeled ice thickness against concentration maps. I have some observations but unfortunately not much insight.

POIMAS definitely shows ice where NSIDC does not, but this could be explained by the 15% threshold. This is not conclusive at all, because posters have pointed out the area around Barrow as inconsistent.

However, it also ignores ice that NSIDC clearly shows, such as shore ice in the Bering Sea. The granularity of the PIOMAS chart is lower, so it could get lost in some sort of averaging, but I am not convinced of that.

As others have said, it seems to have problems with overestimating thinner ice, but I'm seeing it go both ways. It may have similar issues with thick ice, but that's tougher to tell using NSIDC concentration. There are short lived low concentrations (NSIDC) that move across the interior of the ice pack that are not reflected in the morphology of the PIOMAS map thicknesses. I am wondering if some sort of box car averaging is being used.

I am not trying to discredit PIOMAS, but it's important to understand it's limitations and I'm not there yet.

We are obviously moving towards thinner ice, so these anomalies will be more widespread, so if anyone has more insight, I am all ears.

I am not trying to discredit PIOMAS, but it's important to understand it's limitations and I'm not there yet.

PIOMAS is known to be:

1. Not very accurate,

and

2. Better than anything else we've got.

At the beginning of the month I posted some thickness graphs (PIOMAS volume divided by NSIDC Area) of some individual seas. It showed clearly that in at least some of the smaller seas as summer advanced, the data started to look somewhat dodgy. But that when that starts to happen at least it does tell you that the sea is nearly kaput of ice.

So here are 4 thickness graphs. The Chukchi - a fair sized sea that melts in a fairly orderly way.The Greenland Sea - really messy,. so dependent on quantity and nature of what arrives from the Fram StraitBaffin Bay Note the 2000 Average line. That I do NOT understand